Microalga-bacteria Community with High Level Carbon Dioxide Acclimation and Nitrogen-fixing Ability

Area of Science:

• Biotechnology
• Environmental Science
• Microbiology

Background:

• Microalgal cultivation for carbon capture is promising but costly due to nitrogen salt requirements.
• Utilizing atmospheric nitrogen offers a sustainable and economical alternative for microalgal growth.

Purpose of the Study:

• To develop a cost-effective microalgal cultivation method using atmospheric nitrogen.
• To enrich and isolate a microalga-bacteria consortium capable of fixing both CO2 and atmospheric nitrogen under elevated CO2 conditions.

Main Methods:

• Enrichment of a microalga-bacteria community from riverbank biofilms under 10% CO2 and nitrogen-free conditions.
• Isolation of a specific microalgal strain (MP5) belonging to the genus Coelastrella.
• Phylogenetic analysis, PCR-DGGE, and bactericide/bacterial co-culture experiments to elucidate symbiotic relationships.

Main Results:

• Isolation of a novel Coelastrella strain (MP5) capable of growth without nitrogen salts.
• Identification of associated bacteria, some suggested to be diazotrophs, within the enriched community.
• Demonstration of MP5's dependence on bacterial co-cultivation for growth in nitrogen-free media, indicating a symbiotic nitrogen fixation process.

Conclusions:

• A microalga-bacteria consortium was successfully enriched, enabling microalgal growth using atmospheric nitrogen and CO2.
• The isolated microalga (MP5) and associated bacteria form a symbiotic relationship for carbon fixation and nitrogen fixation, respectively.
• This finding presents a significant advancement in reducing microalgal production costs for carbon capture technologies.